Metal-cluster compounds have recently attracted attention in the quest for novel low-dimensional multifunctional semiconductors owing to the structural diversity of metal-cluster geometries and the resulting broken symmetries. Based on first-principles calculations, we proposed a one-dimensional (1D) metal-cluster family of X₄OTe₉I₄ (X = Nb, Ti) nanowires with high stability. Due to differences in the number of valence electrons of the metal atoms (Nb and Ti), these two nanowires exhibit distinct chain structures and physical properties. Our calculations revealed that Nb₄OTe₉I₄ and Ti₄OTe₉I₄ nanowires were direct- and indirect-band-gap semiconductors with moderate gaps of 1.32 and 1.25 eV, respectively. The off-center displacement of Nb ions in the optimized Nb₄OTe₉I₄ nanowire induced intrinsic chain-direction ferroelectric ordering, whereas the Ti₄OTe₉I₄ nanowire with a similar chain structure maintained a stable nonferroelectric structure. The structural evolution of the two nanowires under the tensile strain displayed different behaviors. When the tensile strain was applied, the Nb₄OTe₉I₄ nanowire tended to shrink toward the cluster structure to stabilize the polar structure and produce the unexpected force release, whereas Ti₄OTe₉I₄ nanowire was uniformly stretched before fracture. In addition, tunable magnetism was introduced into these two nonmagnetic 1D systems using carrier doping and alloying methods. On the one hand, the alloying process regulated the band gap of the material; on the other hand, it altered the spin-electronic properties of the system. Our calculations indicate that X₄OTe₉I₄ (X=Nb, Ti) nanowires serve as representative 1D multifunctional materials, which are crucial for studying the structure-determined properties of low-dimensional materials.
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Zhang et al. (2024) studied this question.
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